BR112021013541A2 - ORIENTED GRAIN ELECTRIC STEEL SHEET, AND METHOD TO MANUFACTURE GRAIN ORIENTED ELECTRIC STEEL SHEET - Google Patents

Abstract

grain oriented electrical steel sheet, and method for manufacturing grain oriented electrical steel sheet. this grain-oriented electrical steel sheet comprises a base material steel sheet (1), an intermediate layer (4) provided on the base material steel sheet (1) so as to be in contact therewith , and an insulating coating film (3) provided over the intermediate layer (4), so as to be in contact therewith, said grain-oriented electrical steel sheet which is distinguished by the fact that the surface of the base material steel (1) has a groove (g) that extends in a direction that crosses the rolling direction of the base material steel sheet (1), and, if the region between the ends of the groove (g ) in cross-section in the plane parallel to the rolling direction of the base material steel sheet (1) and the steel thickness direction is defined as a groove part (rg), the average thickness of the intermediate layer (4) in the Groove part (rg) is 0.5 to 3.0 times the average thickness of the middle layer (4) in regions other than the sud part lco (rg), and the area ratio of the voids in the insulating coating film (3) in the groove part (rg) is 15% or less.

Description

1 / 55 ORIENTED GRAIN ELECTRIC STEEL SHEET AND METHOD

TO MANUFACTURE GRAIN ELECTRIC STEEL SHEET

ORIENTED [Technical Field]

[001] The present invention relates to a grain oriented electrical steel sheet with excellent coating adhesion. Particularly, the present invention relates to a grain oriented electrical steel sheet with excellent coating adhesion of an insulating coating without still having a forsterite film.

[002] Priority is claimed in Japanese Patent Application No. 2019-005058, filed January 16, 2019, the contents of which are incorporated herein by reference. [Fundamentals of Technique]

[003] Grain-oriented electrical steel sheets are soft magnetic materials and are mainly used as iron core materials for transformers. Therefore, magnetic properties like high magnetization properties and low iron loss are required. Magnetization properties are magnetic flux densities induced when the iron core is excited. When magnetic flux densities increase, iron core sizes can be reduced, which is advantageous in terms of transformer device constitutions and also in terms of transformer manufacturing costs.

[004] In order to improve the magnetic properties, it is necessary to control a texture so that as many grains as possible are in a crystal orientation (Goss orientation), where the {100} plane is aligned parallel to the surface of sheet steel, and the geometry axis <100> is aligned with the rolling direction. In order to accumulate crystal orientations in the Goss orientation, it is common practice to finely precipitate

2 / 55 inhibitors such as AlN, MnS and MnSe in steel to control secondary recrystallization.

[005] Iron loss is a loss of energy consumed as heat energy when the iron core is excited by an alternating current magnetic field. From an energy saving point of view, it is required that the loss of iron is as little as possible. Magnetic susceptibility, plate thickness, film voltage, amount of impurities, electrical resistivity, grain size, magnetic domain size and the like affect the level of iron loss. Even now that various technologies for electrical steel sheet have been developed, research and development to reduce iron loss is being continued for better energy efficiency.

[006] Other properties required for grain oriented electrical steel sheet are properties of a coating formed on a surface of a base steel sheet. In general, in grain-oriented electrical steel sheets, as shown in FIG. 1, a forsterite film 2 mainly composed of Mg2SiO4 (forsterite) is formed on the base steel sheet 1, and an insulating coating 3 is formed on the forsterite film 2. The forsterite film and the insulating coating have a function of electrically insulate the surface of the base steel plate and apply tension to the base steel plate to reduce iron loss. The forsterite film also contains a small amount of the impurities and additives contained in the base steel sheet and an annealing separator, and reaction products thereof, in addition to Mg2SiO4.

[007] In order for the insulation coating to exhibit the required insulation and voltage properties, the insulating coating should not peel off from the electrical steel sheet. Therefore, the insulation coating is required to have high coating adhesion. However, it is not easy to increase the stress applied to the base steel sheet and the adhesion of

3 / 55 coating at the same time. Even now, research and development to intensify them at the same time continues.

[008] Grain oriented electrical steel sheets are normally manufactured by the following procedure. A silicon steel slab containing 2.0 to 4.0 wt% Si is hot rolled, the steel sheet after hot rolling is annealed as needed, and then the annealed steel sheet is cold rolled once. once or twice or more with intermediate annealing interposed between them to finish the steel sheet to a final thickness. Then, the final thickness steel sheet is annealed by decarburization in a hydrogen atmosphere to promote primary recrystallization in addition to decarburization and to form an oxide layer on the surface of the steel sheet.

[009] An annealing separator containing MgO (magnesia) as a main component is applied to the steel sheet with an oxide layer, dried, and after drying, the steel sheet is wound into a coil format. Next, the coiled steel sheet is annealed at the end to promote secondary recrystallization, and the crystal orientations of the grains are accumulated in the Goss orientation. Furthermore, MgO in the annealing separator is reacted with SiO2 (silica) in the oxide layer to form an inorganic forsterite film mainly composed of Mg2SiO4 on the surface of the base steel sheet.

[0010] Next, the steel sheet with the forsterite film is annealed by purification to diffuse the impurities in the base steel sheet to the outside and to remove them. Furthermore, after the steel sheet is planed annealed, a solution mainly composed of, for example, a phosphate and colloidal silica is applied to the surface of the steel sheet with the forsterite film and baked to form an insulating coating. At this time, stress due to a difference in a coefficient of thermal expansion is applied between the crystalline base steel sheet and the

4 / 55 substantially amorphous insulation coating. Therefore, the insulation coating can be referred to as a voltage coating.

[0011] An interface between the forsterite film composed primarily of Mg2SiO4 (“2” in FIG. 1) and the steel sheet (“1” in FIG. 1) normally has a non-uniform irregular shape (refer to FIG. 1). The uneven interface slightly diminishes the effect of reducing iron loss due to stress. Since iron loss is reduced when the interface is smoothed, further developments have been carried out to date.

[0012] Patent Document 1 describes a manufacturing method in which the forsterite film is removed by a method such as pickling, and the surface of the steel sheet is smoothed by chemical or electrolytic polishing. However, in the manufacturing method of Patent Document 1, it may be difficult for the insulation coating to adhere to the surface of the base steel sheet.

[0013] Therefore, in order to improve the coating adhesion of the insulation coating to the smoothed surface of the steel sheet, as shown in FIG. 2, it has been proposed to form an intermediate layer 4 (or a base film) between the base steel sheet and the insulating coating. A base film described in Patent Document 2 and formed by applying an aqueous solution of an alkali metal phosphate or silicate is also effective in coating adhesion. As a more effective method, Patent Document 3 describes a method in which a steel sheet is annealed in a specific atmosphere before an insulating coating is formed and an externally oxidized silica layer is formed as an intermediate layer on the surface of the sheet. of steel.

[0014] Coating adhesion can be improved by forming an intermediate layer like this, but since it is additionally required

5 / 55 Large-scale equipment, such as electrolytic treatment equipment and dry coating equipment, can be difficult to secure a site for, and the manufacturing cost can increase.

[0015] Patent documents 4 to 6 describe techniques in which, when an insulating coating containing an acidic organic resin as a main component that does not contain substantially chromium is formed on a steel sheet, a layer of phosphorus compound (a layer composed of FePO4, Fe3(PO4)2, FeHPO4, Fe(H2PO4)2, Zn2Fe(PO4)2, Zn3(PO4)2, and hydrates thereof, or a layer composed of a phosphate of Mg, Ca and Al with a thickness of 10 to 200 nm) is formed between the steel sheet and the insulation coating to improve the exterior and adhesion of the insulation coating.

[0016] On the other hand, a magnetic domain control method (which subdivides a 180° magnetic domain), in which a 180° magnetic domain width is narrowed forming stress deformation parts and groove parts in a direction that crosses the rolling direction at predetermined intervals in the rolling direction, is known as a method to reduce anomalous eddy current loss which is a type of iron loss. In one method for forming a stress strain, a 180° magnetic domain refinement effect of a reflux magnetic domain generated in the strain part is used. A representative method is a method using a shock wave or rapid heating by irradiation with a laser beam. In this method, the surface shape of the irradiated portion hardly changes. On the other hand, one method for forming a groove uses an anti-magnetic field effect due to a magnetic pole generated in a side wall of the groove. That is, magnetic domain control is classified into a deformation application type and a groove formation type. For example, Patent Document 7 describes a technique for forming a groove by irradiating with

6 / 55 a laser beam or an electron beam.

[0017] Furthermore, when a transformer with a wound core is fabricated using a grain oriented electrical steel sheet in order to remove a strain stress caused by the grain oriented electrical steel sheet which is wound into a coil shape , it is necessary to carry out a stress-relieving annealing process. When a wound core is fabricated using a grain-oriented electrical steel sheet whose magnetic domain is controlled by a deformation application method, once the deformation disappears by performing the stress-relieving annealing process, the domain refining effect (ie the effect to reduce anomalous eddy current loss) also disappears. On the other hand, when the wound core is manufactured using the grain-oriented electric steel sheet whose magnetic domain is controlled in a groove forming method, since the groove does not disappear even when the stress relief annealing process is performed, the magnetic domain refining effect can be maintained. Therefore, a groove forming type is adopted as a method to manufacture a magnetic domain control material for a wound core. When a stacked core transformer is manufactured, one of the strain application type and the groove forming type can be selectively adopted since stress relief annealing is not performed.

[0018] A method of electrolytic etching (Patent Document 8), in which a groove is formed in a surface of a grain-oriented electric steel sheet by electrolytic etching, a method of gear pressing (Patent Document 9), in which a groove is formed in a surface of a steel sheet by mechanically pressing a gear on the surface of the grain-oriented electrical steel sheet, and a laser radiation method (Patent Document 10), in which a groove is formed in a surface of a grain oriented electrical steel sheet

7 / 55 by laser radiation, are generally known as the groove formation magnetic domain control method.

[0019] In addition, magnetic domain control by groove formation is also performed on a grain oriented electrical steel sheet without any forsterite film as described above. For example, Patent Document 11 describes a fabrication method for forming a groove by pressing a tooth mold onto a sheet steel surface. Patent Document 12 describes a manufacturing method for forming a groove in a surface of a steel sheet by a photoetching method or a method of radiation from a laser, infrared rays, an electron beam or the like. Furthermore, Patent Document 13 describes a manufacturing method in which linear or dotted grooves are formed in a surface of a steel sheet at predetermined intervals before the insulation coating is fired or after the insulation coating is fired.

[0020] [Citation List] [Patent Document] [Patent Document 1] Japanese Unexamined Patent Application, First Publication No. S49-096920 [Patent Document 2] Japanese Unexamined Patent Application, First Publication No. H05-279747 [Document Patent 3] [Patent Document 1] Japanese Unexamined Patent Application, First Publication No. H06-184762 [Patent Document 4] Japanese Unexamined Patent Application, First Publication No. 2001-220683

8 / 55

[Patent Document 5] Japanese Unexamined Patent Application, First Publication No. 2003-193251 [Patent Document 6] Japanese Unexamined Patent Application, First Publication No. 2003-193252 [Patent Document 7] Japanese Unexamined Patent Application, First Publication No. 2012-177164 [Patent Document 8] Japanese Unexamined Patent Application, First Publication No. S62-054873 [Patent Document 9] Japanese Unexamined Patent Application, First Publication No. S62-053579 [Patent Document 10] Japanese Patent Application No. Examined, First Publication No. H06-057335 [Patent Document 11] Japanese Unexamined Patent Application, First Publication No. H08-269554 [Patent Document 12] Japanese Unexamined Patent Application, First Publication No. H08-269557 [Patent Document 13] Application Japanese Patent Unexamined, First Publication No. 2004-342679 [Summary of the Invention] [Problem to be Solved by the Invention]

9 / 55

[0021] Conventionally, the studies described above were done on a technique to reduce iron loss from a grain-oriented electrical steel sheet. Meanwhile, for a grain-oriented electrical steel sheet with a three-layer structure of “middle layer of base steel sheet mainly composed of silicon oxide insulation coating” and without any forsterite film, detailed studies have not been carried out. conducted on adhesion between the intermediate layer and the insulation coating.

[0022] Therefore, as a result of examining the adhesion between the intermediate layer and the insulating coating of the grain-oriented electrical steel sheet, the present inventors have found a problem that when the treatment for magnetic domain control, i.e., the groove described above is formed, the insulation coating is easily peeled off especially around the groove.

[0023] The present invention was made in view of the above problems, and an objective of the same is to provide a grain-oriented electrical steel sheet capable of ensuring good adhesion of an insulating coating and obtaining a good iron loss reduction effect in grain oriented electrical steel sheet which does not have a forsterite film and has grooves formed in a base steel sheet, and a method for making such a grain steel sheet. [Means to Solve the Problem]

[0024] (1) A grain oriented electrical steel sheet according to an aspect of the present invention includes a grain oriented electrical steel sheet with a base steel sheet; an intermediate layer arranged to be in contact with the base steel sheet, and an insulating coating arranged to be in contact with the intermediate layer, and the grain oriented electrical steel sheet includes a surface of the base steel sheet with a groove that extends in a direction that crosses a direction

10 / 55 base steel sheet rolling, where in a cross-sectional view of a plane parallel to the rolling direction and a sheet steel sheet thickness direction of the base sheet, when a region between end portions of groove is defined as a groove part, an average thickness of the middle layer of the groove part is 0.5 times or more and 3.0 times or less an average thickness of the middle layer different from the groove part, and an area ratio of voids in the insulating coating of the groove part is 15% or less.

[0025] (2) In the grain-oriented electrical steel sheet described in (1), in the cross-sectional view, when an internally oxidized part with a maximum depth of 0.2 μm or more is present in the base steel sheet of the Groove part is represented by a line segment ratio at an interface between the base steel sheet and the intermediate layer, the internally oxidized part may be present at 15% or less.

[0026] (3) In the grain-oriented electrical steel sheet described in (1) or (2), in the cross-section view, a depth of the base steel sheet from the surface of the base steel sheet different from the part of groove to a bottom portion of the groove part in the plate thickness direction of the base steel plate is 15 μm or more and 40 μm or less.

[0027] (4) In the grain-oriented electrical steel sheet described in any one of (1) to (3), in the cross-section view, an average thickness of the insulation coating other than the groove part can be 0. 1 μm or more and 10 μm or less, and the depth of the base steel sheet from a surface of the insulating coating of the groove part to a bottom portion of the groove part in the sheet thickness direction of the groove part. base steel can be 15.1 μm or more and 50 μm or less.

[0028] (5) In the grain-oriented electrical steel sheet described in any one of (1) to (4), the groove may be provided either continuously or discontinuously when viewed in a direction perpendicular to a surface of

11 / 55 sheet steel base plate.

[0029] (6) A method for manufacturing a grain-oriented electrical steel sheet in accordance with an aspect of the present invention is a method for manufacturing the grain-oriented electrical steel sheet described in any one of (1) to (5) ), the method includes forming a groove in the base steel sheet that does not have a forsterite film and has a texture developed in a {110}<001> orientation at any stage after cold rolling and before the insulation coating is formed on the base steel sheet, and form the intermediate layer and the insulation coating on the base steel sheet after the groove is formed, wherein in forming the insulation coating, an insulation coating forming solution is applied to the sheet of base steel, and the base steel sheet is soaked in a temperature range of 800°C or greater and 1000°C or less for 10 seconds or more and 120 seconds or less in an atmospheric gas containing hydrogen and nitrogen and with an oxidation degree of PH2O/PH adjusts 0.001 or more and 0.15 or less, and the embedded base steel sheet is cooled to 500°C at a cooling rate of 5°C/s or more and 30°C/s or less.

[0030] (7) A method for manufacturing a grain-oriented electrical steel sheet according to an aspect of the present invention is a method for manufacturing the grain-oriented electrical steel sheet described in any one of (1) to (5) ), the method includes forming the intermediate layer and insulation coating on the base steel sheet which does not have a forsterite film and has a texture developed in a {110}<001> orientation, forming a groove in the steel sheet of base on which the intermediate layer and the insulating coating are formed, and additionally forming the intermediate layer and the insulating coating on the base steel sheet on which the groove is formed, wherein, in at least the final formation of the coating of insulation, an insulating coating forming solution is applied to the base steel sheet, and the base steel sheet is embedded in a strip of

12 / 55 temperature of 800°C or greater and 1000°C or less for 10 seconds or more and 120 seconds or less in an atmospheric gas containing hydrogen and nitrogen and with an oxidation degree of PH2O/PH set to 0.001 or more and 0.15 or less, and the embedded steel base plate is cooled to 500°C at a cooling rate of 5°C/s or more and 30°C/s or less. [Effects of Invention]

[0031] According to the present invention, it is possible to provide a grain-oriented electrical steel sheet capable of ensuring good adhesion of an insulating coating and to obtain a good iron loss reduction effect in grain-oriented electrical steel sheets that does not have a forsterite film and has grooves formed in a base steel sheet, and a method for making such a grain steel sheet. [Brief Description of Drawings]

[0032] FIG. 1 is a schematic cross-sectional view showing a cladding structure of a conventional grain oriented electrical steel sheet.

[0033] FIG. 2 is a schematic cross-sectional view showing a conventional grain oriented electrical steel sheet cladding structure.

[0034] FIG. 3 is a schematic cross-sectional view for explaining a groove portion of a grain-oriented electrical steel sheet in accordance with an embodiment of the present invention.

[0035] FIG. 4 is an example of an SEM image of a cross-section of modality-oriented grain-oriented electrical steel sheet.

[0036] FIG. 5 is a diagram to explain a definition of a line segment ratio of an internally oxidized part in grain oriented electrical steel sheet according to embodiment. [Modalities for Implementing the Invention]

13 / 55

[0037] As a result of detailed observation using an electron microscope or the like, the present inventors have found that even in a conventional insulating coating with excellent coating adhesion, when a groove is formed in a surface of a steel sheet base to For the purpose of controlling a magnetic domain, the insulation coating is partially peeled.

[0038] As a result of repeated observations and verifications, the present inventors have found that when a groove is formed in a surface of the base steel sheet, cracks occur in the insulation coating formed within the groove, and the cracks cause voids or internal oxidation in the base steel plate. In particular, when the groove was deeply formed in the base steel sheet without any forsterite film, the occurrence of cracks was noticeable. This is thought to be because the insulation coating inside the groove part becomes thicker than the insulation coating other than the groove, and stress concentration occurs.

[0039] Additionally, the present inventors have found that peeling occurs at an interface between the insulation coating and the intermediate layer starting from voids and internally oxidized parts.

[0040] Furthermore, as a result of examining properties of the cracks, the present inventors have found that the cracks generated in the insulation coating formed within the groove depend on conditions for forming the insulation coating.

[0041] Hereinafter, preferred embodiments of the present invention will be described. However, it is obvious that the present invention is not limited to configurations described in the embodiments, and various modifications can be made without departing from the scope of the present invention. It is also obvious that the elements of the following modalities can be combined

14 / 55 with each other within the scope of the present invention.

[0042] Also, in the following embodiments, a numerical limitation range represented using “to” means a range that includes numerical values before and after “para” as a lower limit value and an upper limit value. Numerical values indicated by “greater than” or “less than” are not included in their numerical range. [Electrical Grain Oriented Steel Sheet]

[0043] A grain oriented electrical steel sheet in accordance with the present embodiment has a base steel sheet, an intermediate layer arranged to be in contact with the base steel sheet, and an insulating coating arranged to be in contact with the base steel sheet. contact with the middle layer.

[0044] The grain-oriented electrical steel sheet, according to the present embodiment, has a groove that extends in a direction that crosses a rolling direction of the base steel sheet on a surface of the base steel sheet, and when a region between groove end portions is defined as a groove part, an average thickness of an intermediate layer of the groove part is 0.5 times or more and 3.0 times or less an average thickness of the different intermediate layer of the groove part, and an area ratio of voids in the insulating coating of the groove part is 15% or less in a cross-sectional view of a plane parallel to the rolling direction and a sheet thickness direction of the grooving plate. base steel.

[0045] In the grain-oriented electrical steel sheet, according to the present embodiment, there is a base steel sheet, an intermediate layer arranged to be in contact with the base steel sheet, and an insulating coating arranged to be in contact with the intermediate layer, and there is no forsterite film.

[0046] Here, the grain-oriented electric steel sheet without a

15 / 55 forsterite film is a grain-oriented electric steel sheet manufactured by removing the forsterite film after production, or a grain-oriented electric steel sheet manufactured by suppressing the formation of a forsterite film.

[0047] In the present embodiment, the rolling direction of the base steel sheet is a rolling direction in the hot rolled or cold rolled when the base steel sheet is manufactured by a manufacturing method that will be described later. The rolling direction may also be referred to as a sheet passing direction, a conveying direction or the like of a steel sheet. The rolling direction is a longitudinal direction of the base steel sheet. The lamination direction can also be identified using a device to observe a magnetic domain structure or a device to measure a crystal orientation such as an X-ray Laue method.

[0048] In the present embodiment, the direction crossing the rolling direction means a direction in a range of inclination within 45° in a clockwise or counterclockwise direction parallel to the surface of the base steel sheet from a parallel direction or perpendicular to the surface of the base steel sheet with respect to the rolling direction (hereinafter, it is also simply referred to as a “direction perpendicular to the rolling direction”). Once the groove is formed on the surface of the base steel sheet, the groove extends from a direction perpendicular to the rolling direction and the sheet thickness direction on the surface of the base steel sheet to a direction of 45° inclination on the plate surface of the base steel plate.

[0049] The plane parallel to the rolling direction and the sheet thickness direction means a plane parallel to both the rolling direction and sheet thickness direction of the base steel sheet described above.

16 / 55

[0050] Hereinafter, each of the constituent components of the grain-oriented electrical steel sheet according to the present embodiment will be described. (base steel sheet)

[0051] The base steel sheet which is a base material has a texture where a crystal orientation is controlled so that it becomes a Goss orientation on the surface of the base steel sheet. A surface roughness of the base steel sheet is not particularly limited, but an arithmetic mean roughness (Ra) thereof is preferably 0.5 μm or less, and more preferably 0.3 μm or less to apply large stress to the steel plate. base steel to reduce iron loss. A lower limit of the arithmetic mean roughness (Ra) of the base steel sheet is not particularly limited, but when it is 0.1 μm or less, an iron loss improving effect becomes saturated, and so the lower limit can be 0.1 μm.

[0052] A plate thickness of the base steel plate is also not particularly limited, but an average plate thickness thereof is preferably 0.35 mm or less, and more preferably 0.30 mm or less to further reduce loss of iron. A lower limit on the sheet thickness of the base steel sheet is not particularly limited, but it can be 0.10 mm from a manufacturing equipment and cost point of view. A method for measuring the sheet thickness of the base steel sheet is not particularly limited, but it can be measured using, for example, a micrometer or the like.

[0053] A chemical composition of the base steel sheet is not particularly limited, but preferably includes, for example, a high concentration of Si (eg, 0.8 to 7.0% by mass). In this case, a strong chemical affinity develops between the base steel sheet and the intermediate layer composed mainly of a silicon oxide, and the

17 / 55 the middle layer and the base steel plate are adhered to each other. The detailed chemical composition of the base steel sheet 11 will be described later. (middle layer)

[0054] The intermediate layer is arranged to be in contact with the base steel sheet (i.e. formed on the surface of the base steel sheet) and has a function of placing the base steel sheet and the insulation coating in close contact with each other. The intermediate layer extends continuously on the surface of the base steel sheet. The adhesion between the base steel sheet and the insulation coating is improved and stress is applied to the base steel sheet forming the intermediate layer between the base steel sheet and the insulation coating.

[0055] The intermediate layer can be formed by heat treatment, a base steel sheet from which the forsterite film formation is suppressed during final annealing or a base steel sheet from which the forsterite film is removed after final annealing in an atmospheric gas adjusted to a predetermined degree of oxidation.

[0056] Silicon oxide, which is a major component of the intermediate layer, is preferably SiOx (x=1.0 to 2.0). When the silicon oxide is SiOx (x=1.0 to 2.0), the silicon oxide is more stable, which is more preferable.

[0057] For example, when a heat treatment is carried out under atmospheric gas conditions: 20 to 80% N2+ 80 to 20% H2 (100% in total), a dew point: -20 to 2°C, an annealing temperature: 600 to 1150°C, and an annealing time: 10 to 600 seconds, an intermediate layer composed mainly of a silicon oxide can be formed.

[0058] When an intermediate layer thickness is thin, a thermal stress relaxation effect can be sufficiently exhibited. Therefore, the thickness of the intermediate layer is preferably 2 nm or

18 / 55 more on average. The thickness of the intermediate layer is more preferably 5 nm or more. On the other hand, when the thickness of the middle layer is thick, the thickness becomes non-uniform, and defects such as voids and cracks can occur in one layer. Furthermore, the thickness of the intermediate layer is preferably 400 nm or less, and more preferably 300 nm or less. A method for measuring the thickness of the intermediate layer will be described later.

[0059] The intermediate layer may be an externally oxidized film formed by external oxidation. Externally oxidized film is an oxide film formed in an atmospheric gas with a low degree of oxidation and means an oxide formed in a film form on the surface of the steel sheet after an alloying element (Si) in the steel sheet is diffused. to the surface of the steel sheet.

[0060] As described above, the intermediate layer contains silica (silicon oxide) as a main component. In addition to the silicon oxide, the intermediate layer may contain an oxide of an alloying element contained in the base steel sheet. That is, it may contain any oxide of Fe, Mn, Cr, Cu, Sn, Sb, Ni, V, Nb, Mo, Ti, Bi and Al, or a composite oxide thereof. The intermediate layer may also contain metal grains of Fe or the like. Also, the middle layer may contain impurities while the effect is not impaired.

[0061] In grain-oriented electric steel sheet, according to the present embodiment, an average thickness of the intermediate layer in a groove part is 0.5 times or more and 3.0 times or less an average thickness of the intermediate layer different from the groove part.

[0062] With such a configuration, good adhesion of the insulation coating can be maintained even in the groove part.

[0063] An average thickness of the intermediate layer other than the deformation region can be measured with an electron microscope of

19 / 55 scanning (SEM) or a transmission electron microscope (TEM) by a method that will be described later. Furthermore, an average thickness of the intermediate layer in the groove part can also be measured by the same method.

[0064] Specifically, the average thickness of the intermediate layer in the groove part and the average thickness of the intermediate layer other than the groove part can be measured by the method described below.

[0065] First, a test piece is cut so that a cutting direction is parallel to the sheet thickness direction (specifically, the test piece is cut so that a cut surface is parallel to the sheet thickness direction and perpendicular to the rolling direction), and a cross-sectional structure of the cut surface is observed by the SEM at a magnification where each of the layers (i.e. the base steel sheet, the middle layer, and the insulation cladding) is included in an observation field of view. It is possible to infer how many layers the cross-sectional structure includes by looking with a backscattered electron composite image (a COMPO image).

[0066] In order to identify each of the layers in the cross-sectional structure, a line analysis in the sheet thickness direction is performed using an energy dispersive X-ray spectroscopy (SEM-EDS), and a quantitative analysis of the composition. chemistry of each of the layers is performed.

[0067] The elements to be analyzed quantitatively are five elements of Fe, Cr, P, Si and O. “Atomic %” described below is not an absolute value of atomic %, but a relative value calculated based on an intensity of X-rays corresponding to the five elements.

[0068] In the following, it is assumed that the relative value measured by SEM-EDS is a specific numerical value obtained by performing a line analysis with a scanning electron microscope (NB5000) manufactured by

20 / 55 Hitachi High-Technologies Corporation and an EDS analyzer (XFlash(r) 6|30) manufactured by Bruker AXS GmbH. and providing the results thereof to EDS data software (ESPRIT 1.9) manufactured by Bruker AXS GmbH. for calculation.

[0069] Also, the relative value measured by the TEM-EDS must be a specific numerical value obtained by performing a line analysis with a scanning electron microscope (JEM-2100F) manufactured by EOL Ltd. and an X-ray power analyzer dispersive (JED-2300T) manufactured by JEOL Ltd. and providing the results thereof to the EDS data software (an analysis station) manufactured by JEOL Ltd. for calculation. Of course, measurement with SEM-EDS and TEM-EDS is not limited to the examples shown below.

[0070] First, the base steel sheet, the intermediate layer and the insulating cladding are identified as follows based on the observation results of the COMPO image and the quantitative analysis results of SEM-EDS. That is, when there is a region where an Fe content is 80% atomic or more and an O content is less than 30% atomic excluding measurement noise, and also a line segment (a thickness) or a line of line analysis scan that corresponds to this region is 300 nm or more, this region is determined as the base steel sheet, and regions that exclude the base steel sheet are determined as the intermediate layer and insulation cladding .

[0071] As a result of looking at the region excluding the base steel plate identified above, when there is a region where a P content is 5% atomic or more, and the O content is 30% atomic or more excluding noise measurement, and also the line segment (the thickness) in the scan line of the line analysis that corresponds to this region is 300 nm or more, this region is determined as the insulation coating.

[0072] When the region described above, which is the coating of

21 / 55 isolation, is identified, precipitates or inclusions contained in the film are not included in targets for determination, and a region that satisfies the quantitative analysis results described above, as a matrix phase is determined as the insulating coating. For example, when it is confirmed from the COMPO image or the line analysis results that precipitates or inclusions are present in the line analysis scan line, the determination is made based on the quantitative analysis results, as the phase of matrix without this region being included in the targets. The precipitates or inclusions can be distinguished from the matrix phase by a contrast in the COMPO image and can be distinguished from the matrix phase by the amount of constituent elements present in the quantitative analysis results.

[0073] When there is the region that excludes the base steel sheet and insulation coating identified above, and the line segment (the thickness) in the line analysis scan line that corresponds to that region is 300 nm or further, this region is determined as the middle layer. The middle layer can satisfy an average Si content of 20 atomic% or more and an average O content of 30 atomic% or more as a global average (e.g. the arithmetic mean of the atomic % of each of the elements measured at each one of the measurement points on the scan line). The intermediate layer quantitative analysis results are quantitative analysis results such as the matrix phase, which does not include analysis results of the precipitates or inclusions contained in the intermediate layer.

[0074] The identification of each of the layers and the thickness measurement by the above-described COMPO image observation and SEM-EDS quantitative analysis are performed at five or more locations with different observation fields of view. An arithmetic mean value is obtained from values that exclude a maximum value and a minimum value

22 / 55 between the thickness of the layers obtained in five or more locations in total, and this average value is used according to the thickness of each of the layers. However, the thickness of the oxide film that is the intermediate layer is measured at a location where it can be determined that it is an external oxidation region and not an internal oxidation region while a morphology is observed, and an average value of the same is obtained. The thickness (the average thickness) of the insulation coating and the intermediate layer can be measured by such a method.

[0075] When there is a layer where the line segment (the thickness) in the line analysis scan line is less than 300 nm in at least one of the five or more observation fields of view described above, a corresponding layer is observed in detail with the TEM, and the identification of the corresponding layer and the measurement of the thickness are carried out by the TEM. More specifically, a test part that includes a layer to be observed in detail using TEM is cut by focused ion beam (FIB) processing so that a cut direction is parallel to the sheet thickness direction (specifically, the part test is cut so that a cut surface is parallel to the sheet thickness direction and perpendicular to the rolling direction), and the cross-sectional structure of that cut surface (a brightfield image) is observed by scanning TEM (STEM). ) at a magnification where the corresponding layer is included in the observation field of view. When each of the layers is not included in the observation field of view, the cross-sectional structure is observed in a plurality of continuous fields of view.

[0076] In order to identify each of the layers in the cross-sectional structure, line analysis is performed in the sheet thickness direction using TEM-EDS, and quantitative analysis of the chemical composition of each of the layers is performed. The elements to be analyzed from

23 / 55 quantitatively, there are five elements Fe, Cr, P, Si and O.

[0077] Each of the layers is identified and the thickness of each of the layers is measured based on the TEM brightfield image observation results and the TEM-EDS quantitative analysis results described above. The method for identifying each of the layers and the method for measuring the thickness of each of the layers using TEM can be performed according to the method described above using SEM.

[0078] When the thickness of each of the layers identified by the TEM is 5 nm or less, it is preferable to use a TEM with a spherical aberration correction function from the point of view of a spatial resolution. Furthermore, when the thickness of each of the layers is 5 nm or less, a point analysis can be performed in the sheet thickness direction at intervals of, for example, 2nm or less, the line segment (the thickness) of each of the layers can be measured, and this line segment can be adopted as the thickness of each of the layers. For example, when the TEM with spherical aberration correction function is used, an EDS analysis can be performed with the spatial resolution of about 0.2 nm.

[0079] In the method described above to identify each of the layers, once the base steel sheet in the entire region is identified first, then the insulation coating on a remnant is identified, and finally the remainder is determined as the layer intermediate, in the case of a grain-oriented electrical steel sheet satisfying the configuration of the present embodiment, there is no unidentified region different from each of the layers described above in the entire region. (insulation coating)

[0080] Insulation coating is a glassy insulating coating formed by applying a solution primarily composed of a phosphate and colloidal silica (SiO2) to the surface of the layer

24 / 55 intermediate and baking it. Alternatively, a solution primarily composed of alumina sol and boric acid can be applied to the surface of the interlayer and baked to form an insulating coating. The insulation coating can provide high surface tension to the base steel sheet. The insulating coating constitutes, for example, the outermost surface of the grain-oriented electrical steel sheet.

[0081] The average thickness of the insulation coating is preferably from 0.1 to 10 μm. When the insulation coating thickness is less than 0.1 μm, the coating adhesion of the insulation coating may not be improved, and it may be difficult to apply the required surface tension to the steel sheet. Therefore, the thickness is preferably 0.1 µm or more, and more preferably 0.5 µm or less on average.

[0082] When the average thickness of the insulation coating is more than 10 μm, cracks may occur in the insulation coating in the stage to form the insulation coating. Therefore, the average thickness is preferably 10 nm or less, and more preferably 5 nm or less on average.

[0083] In consideration of recent environmental problems, an average Cr concentration in the insulation coating is preferably limited to less than 0.10% atomic, and more preferably limited to less than 0.05% atomic as the chemical composition.

[0084] In grain-oriented electrical steel sheet, according to the present embodiment, the average thickness of the insulating coating other than the groove part can be 0.1 μm or more and 10 μm or less, and more preferable, a depth of the base steel sheet from the surface of the insulating coating of the groove part to a bottom portion of the groove part in the sheet thickness direction is 15.1 μm or more and 50 μm or less.

[0085] With a configuration like this, it is possible to obtain a

25 / 55 in which good adhesion and iron loss properties of the insulation coating can be obtained at the same time. (Groove)

[0086] The groove formed in the base steel sheet will be described with reference to FIG. 3. As shown in FIG. 3, a groove G is formed on the surface of the base steel sheet 1 of the grain oriented electrical steel sheet in accordance with the present embodiment. FIG. 3 is a schematic view showing a cross-section of the base steel sheet 1 parallel to the rolling direction and the sheet thickness direction. The intermediate layer 4 shown in FIG. 2 is formed on the base steel sheet 1. Since the intermediate layer 4 has a smaller thickness than those of the other layers, the intermediate layer 4 is represented by a line in FIG. 3. Insulating coating 3 is formed on the middle layer 4.

[0087] As shown in FIG. 3, a straight line s' is a straight line that is 1 μm from the base steel plate 1 with a straight line s along a surface in a region where the groove G of the base steel plate 1 is not formed and is parallel to the straight line s. As shown in FIG. 3, an intersection of an inclined surface of groove G and the straight line s' is defined as an end portion e or an end portion e' of groove G.

[0088] The straight line s can be determined by a method shown in FIG. 3, for example, based on an image of a SEM photograph or a TEM photograph. That is, a portion where an interface between the base steel sheet 1 and the insulation coating 3 is substantially horizontal (the region where the groove G is not formed) is identified by looking at the SEM photograph images and the photograph of MET. So a straight line that passes through an interface like this and is horizontal is defined as the straight line s.

[0089] A G groove width WG is defined as the distance between

26 / 55 the end portion and the end portion is in a direction parallel to the surface of the region in which the groove G of the base steel plate 1 is not formed. Furthermore, in a direction orthogonal to the straight line s, a point on a sloped surface of the groove G farthest from the straight line s is defined as a bottom b portion of the groove G. The shortest distance from the bottom b portion to the straight line s' is defined as a depth DG of groove G.

[0090] In the cross section as shown in FIG. 3, a region surrounded by a straight line m that passes through the end portion and is orthogonal to the straight line if a straight line m' that passes through the end portion e' and is orthogonal to the straight line s is referred to as a part of sulcus RG. That is, in FIG. 3, the insulation lining 3 of the groove part RG is a region of the insulation lining 3 is interposed between the straight line m passing through the end portion ee and is orthogonal to the straight line s and the straight line m' passing through the portion end e' e is orthogonal to the straight line s. Furthermore, the insulation coating 3 other than the groove part RG means a region of the insulation coating 3 which excludes the insulation coating 3 described above from the groove part R in FIG. 3.

[0091] The direction orthogonal to the straight line s can be parallel to the sheet thickness direction of the base steel sheet 1.

[0092] Normally, since the grooves are formed at predetermined intervals along the rolling direction in the direction that crosses the rolling direction, a plurality of grooves G are formed intermittently in the rolling direction. Thus, a region between the Nth part of the groove counted in the rolling direction and, for example, the N+1th part of the groove (or N-1th part of the groove) adjacent to the Nth part of the groove in the rolling direction can be referred to as a region different from the groove part.

[0093] The width WG of the groove G is preferably 10 μm or more and

27 / 55 more preferably 20 µm or more. The width WG of the groove G is preferably 500 µm or less and more preferably 100 µm or more.

[0094] In the grain-oriented electrical steel sheet according to the present embodiment, the area ratio of voids in the insulating coating of the groove part is 15% or less. With such a configuration, the effect that the insulation coating adhesion is good can be obtained. The lower limit value of the area ratio of the voids is not particularly limited and can be as low as 0%.

[0095] The area ratio of the voids in the insulating coating of the groove part described above can be identified by the following method.

[0096] The insulation coating identified by the method described above is observed by TEM (a brightfield image). In this brightfield image, a white region becomes a vacuum. Whether the white region is a vacuum or not can be clearly determined by, for example, an EDS analysis of SEM or TEM. The area ratio of the voids in the insulation lining in the groove part described above can be obtained by binarizing the vacuum region and the non-vacuum region in the insulation lining in the observation field of view and performing an analysis of Image. More specifically, a ratio of the number of pixels that are binarized to white to the number of pixels in the insulating coating region of the groove part (the insulating coating region 3 interposed between the straight line m and the straight line m') is defined as the vacuum area ratio.

[0097] In binarizing an image to perform image analysis, the image can be binarized by manually vacuum coloring without a structure photograph based on the vacuum discrimination result described above.

[0098] For the same part of the groove, the area ratio of the voids is measured at the three or more locations with an interval of 50 mm or more in the

28 / 55 direction perpendicular to the rolling direction and the sheet thickness direction of the base steel sheet, and an arithmetic mean value of these area ratios is taken as the area ratio of the voids in the insulating coating of the groove part.

[0099] In the groove part, there may be a cast part formed by melting the base steel plate by irradiation with a laser beam or the like. The area ratio of the voids is defined by an area of the voids in the groove part to an area of the insulation coating including the voids except such a molten part.

[00100] FIG. 4 shows an example of an SEM image of the cross-section of grain-oriented electrical steel sheet (a plane parallel to the rolling direction and sheet thickness direction of the base steel sheet) taken with a part of the groove in the field of vision. In the image of FIG. 4, the cracks in the insulation coating appear white.

[00101] In the grain-oriented electrical steel sheet, according to the present embodiment, in the cross-sectional view of the plane parallel to the rolling direction and to the sheet thickness direction of the base steel sheet, more preferably, the depth DG (i.e. the shortest distance from the base portion of the straight line s') in the sheet thickness direction of base steel plate 1 from the surface of base steel plate 1 other than the groove part RG to the base portion b of the RG groove part is 15 μm or more and 40 μm or less. The DG depth is more preferably 20 µm or more, and the DG depth is more preferably 40 µm or less.

[00102] With such a setup, an effect, where the magnetic domain is subdivided and the iron loss is reduced, can be obtained. When the DG depth is too large, the intermediate layer the internally oxidized layer becomes deep, and voids are likely to be generated in the insulation coating, and the adhesion of the insulation coating may deteriorate.

29 / 55

[00103] In the grain-oriented electrical steel sheet, according to the present embodiment, more preferably, the groove G is provided continuously or discontinuously when viewed in a direction perpendicular to the sheet surface of the base steel sheet 1. The fact that the groove G is provided continuously means that the groove is formed for 5 mm or more in the direction that crosses the rolling direction of the base steel plate 1. The fact that the groove G is provided discontinuous means that a dot-shaped G groove or an intermittent linear G groove of 5 mm or less is formed in the direction that crosses the rolling direction of the base steel sheet 1.

[00104] With such a configuration, an effect, where the magnetic domain is subdivided and the iron loss is reduced, can be obtained. (Part internally oxidized)

[00105] In the grain-oriented electrical steel sheet, according to the present embodiment, an internally oxidized part may be present between the base steel sheet and the intermediate layer. The internally oxidized part is an oxidized region formed in an atmospheric gas with a relatively high degree of oxidation, and is an oxidized region formed in an island shape within the base steel sheet with almost no diffusion of alloying elements into the steel plate. base steel.

[00106] This internally oxidized part has a shape where it is fitted from the interface between the base steel plate and the intermediate layer towards the side of the base steel plate when viewed on a cut surface whose cutting direction is parallel to the sheet thickness direction. This internally oxidized part is formed by an oxidized region that grows from the intermediate layer near the interface as a starting point towards the base steel sheet.

[00107] For example, when an internally oxidized part is

30 / 55 formed on a surface other than the groove part on the surface of the base steel plate, the smoothness of the surface of the base steel plate is impaired, and the loss of iron increases. Therefore, as the area fraction of internally oxidized parts becomes smaller, it is more preferable. In particular, an internally oxidized part perpendicular to the interface and with a maximum depth of 0.2 μm or more from the interface to the base steel plate greatly impairs the smoothness of the surface of the base steel plate and worsens the loss of strength. iron. Therefore, it is preferable to reduce the internally oxidized part to a maximum depth of 0.2 μm or more.

[00108] Although the internally oxidized part can grow to a maximum depth of about 0.5 μm according to manufacturing conditions, the effect that the loss of iron is not deteriorated can be obtained by adjusting the upper limit of the maximum depth of the oxidized region of interest at 0.2 μm.

[00109] Although the cause of the formation of the internally oxidized part within the base steel sheet is not clear, it is assumed that when the insulation coating is formed on the surface of the intermediate layer, some of a phosphoric acid and the like contained in the insulation coating is decomposed, water vapor or oxygen generated during decomposition internally oxidizes the base steel sheet, and thus the internally oxidized part is generated. Alternatively, it is assumed that the conditions of the insulation coating formation process also affect the generation of the internally oxidized part.

[00110] Similar to the intermediate layer, the internally oxidized part contains silica (silicon oxide) as a main component. In addition to the silicon oxide, the internally oxidized part may contain an oxide of an alloying element contained in the base steel sheet. That is, it may contain any oxide of Fe, Mn, Cr, Cu, Sn, Sb, Ni, V, Nb, Mo, Ti, Bi and Al, or a composite oxide thereof. The internally oxidized part can also

31 / 55 contain metal grains of Fe or the like in addition to them. In addition, the internally oxidized part may contain impurities.

[00111] On grain-oriented electrical steel sheet, according to the present embodiment, in a cross-sectional view of a plane parallel to the thickness direction of the base steel sheet, when an internally oxidized part with a maximum depth of 0.2 μm or more present in the base steel sheet of the groove part is expressed as a line segment ratio at the interface between the base steel sheet and the intermediate layer, may be present in an amount of 15% or any less.

[00112] It is possible to preferably suppress the peeling of the insulation coating particularly in the groove part by controlling the generation rate of the internally oxidized part in this way.

[00113] Next, the line segment ratio to define the generation rate of the internally oxidized part in the groove part will be described with reference to FIG. 5. FIG. 5 is a diagram showing the cross-section of the grain electrical steel sheet oriented in a plane parallel to the rolling direction and the sheet thickness direction of the base steel sheet. FIG. 5 is a schematic view, and since the intermediate layer is very thin, the intermediate layer present between the insulation coating 3 and the base steel sheet 1 is omitted.

[00114] As shown in FIG. 5, the line segment ratio representing the generation rate of the internally oxidized part 5 is defined as follows. That is, when looking at the described cross section, a line L, which is 0.2 μm from the interface 6 between the insulation coating 3 and the intermediate layer 4 (refer to FIG. 3) in the groove part and surrounding of them towards the base steel plate and follows the interface 6, is defined. So, the ratio of a total value of a length dn of a strip 5a, where the internally oxidized parts 5 are present in a line segment to a length 1 of a portion (the line segment)

32 / 55 present between the end portions ee e' of the groove in the line L, is defined as a line segment ratio of the internally oxidized part 5. Specifically, the line segment ratio of the internally oxidized part 5 is defined as a percentage of a value obtained by dividing the total value (Σdn=d1+d2+...+dn) of the length dn of the internally oxidized part 5 by the length 1 of the line segment present between the end portions ee e' of the groove. That is, the line segment ratio (%)=(Σdn/l)×100. The line described above L is specifically a set of points on a normal line of a curved or straight line representing interface 6 that passes through a certain point on interface 6 and is 0.2 μm from that point, and is a curved line or straight.

[00115] Furthermore, the length dn of each of the internally oxidized portions 5 is a length of the range 5a where the internally oxidized portion 5 in line L is present. Furthermore, the internally oxidized part 5 to be measured is an internally oxidized part 5 with a maximum depth of 0.2 μm or more from the interface 6.

[00116] With respect to the grain-oriented electrical steel sheet according to the present embodiment, a component composition of the base steel sheet is not particularly limited. Here, since the grain oriented electrical steel sheet is manufactured through various processes, component compositions of material sheet parts (slabs) and base steel sheets which are preferable to manufacture the grain electrical steel sheet oriented according to the present modality will be described below.

[00117] Hereinafter, % with respect to the component composition of the material steel part and the base steel plate means % by mass with respect to a total mass of the material steel part or the base steel plate . (Base steel plate component composition)

[00118] The base steel plate of the electric steel plate, according to

33/55 with the present invention, contains, for example, Si: 0.8 to 7.0%, and is limited to C: 0.005% or less, N: 0.005% or less, a total amount of S and Se: 0.005% or less, and acid-soluble Al: 0.005% or less, and a remainder thereof is composed of Fe and impurities. Si: 0.8% or more and 7.0% or less.

[00119] Silicon (Si) increases electrical resistance of grain-oriented electrical steel sheet and reduces iron loss. The lower limit of the Si content is preferably 0.8% or more, and more preferably 2.0% or more. On the other hand, when the Si content exceeds 7.0%, the saturation magnetic flux density of the base steel sheet decreases, and thus it may be difficult to reduce an iron core size. Therefore, the upper limit of the Si content is preferably 7.0% or less. C: 0.005% or less

[00120] Since carbon (C) forms a compound in the base steel sheet and deteriorates the loss of iron, it is preferable to reduce an amount of it. The C content is preferably limited to 0.005% or less. The upper limit of the C content is preferably 0.004% or less, and more preferably 0.003% or less. Since it is more preferable to reduce the amount of C, the lower limit includes 0%. However, when the amount of C is reduced to less than 0.0001%, the manufacturing cost will increase significantly. Thus, 0.0001% is a practical lower limit in manufacturing. N: 0.005% or less

[00121] Since nitrogen (N) forms a compound in the base steel sheet and deteriorates iron loss, it is preferable to reduce an amount of it. The N content is preferably 0.005% or less. The upper limit of the N content is preferably 0.004% or less, and more preferably 0.003% or less. Since it is more preferable to reduce the amount of N, the lower limit may be 0%.

34 / 55 Total amount of S and Se: 0.005% or less

[00122] Since sulfur (S) and selenium (Se) form a compound in the base steel sheet and deteriorate the loss of iron, it is preferable to reduce an amount of it. The total of one or both S and Se is preferably limited to 0.005% or less. The total amount of S and Se is preferably 0.004% or less, and more preferably 0.003% or less. Since it is more preferable to reduce the amounts of S or Se, the lower limit may be 0%. Acid-soluble Al: 0.005% or less

[00123] Since acid-soluble Al (acid-soluble aluminum) forms a compound in the base steel sheet and deteriorates the loss of iron, it is preferable to reduce an amount of it. The acid soluble Al is preferably 0.005% or less. The acid-soluble Al is preferably 0.004% or less, and more preferably 0.003% or less. Since it is more preferable to reduce acid-soluble Al, the lower limit may be 0%.

[00124] The remainder in the base steel sheet component composition is composed of Fe and impurities. “Impurities” refer to those mixed from ore, scrap, manufacturing environment and the like as raw materials when steel is industrially manufactured.

[00125] In addition, the base steel sheet of the grain-oriented electric steel sheet according to the present embodiment may contain at least one selected from, for example, Mn (manganese), Bi (bismuth), B (boron), Ti (titanium), Nb (niobium), V (vanadium), Sn (tin), Sb (antimony), Cr (chromium), Cu (copper), P (phosphorus), Ni (nickel) and Mo (molybdenum) as a selective element in place of part of Fe which is the remainder to an extent that the properties thereof are not impaired.

[00126] An amount of the selective element described above can be, for example, as follows. The lower limit of the selected element is not particularly limited, and the lower limit can be 0%. Furthermore,

35 / 55 even when the selective element is contained as impurities, the effect of electric steel sheet according to the present invention is not impaired.

[00127] Mn: 0% or more and 1.00% or less, Bi: 0% or more and 0.010% or less, B: 0% or more and 0.008% or less, Ti: 0% or more and 0.015% or less, Nb: 0% or more and 0.20% or less, V: 0% or more and 0.15% or less, Sn: 0% or more and 0.30% or less, Sb: 0% or less plus and 0.30% or less, Cr: 0% or more and 0.30% or less, Cu: 0% or more and 0.40% or less, P: 0% or more and 0.50% or less , Ni: 0% or more and 1.00% or less, and Mo: 0% or more and 0.10% or less.

[00128] The above described chemical composition of the base steel sheet can be measured by a general analysis method. For example, a steel component can be measured using an inductively coupled plasma atomic emission spectrum (ICP-AES). C and S can be measured using a combustion infrared absorption method, N can be measured using an inert gas melting thermal conductivity method, and O can be measured using a gas melting non-dispersive infrared absorption method inert.

[00129] The base steel sheet of the grain-oriented electrical steel sheet, according to the present embodiment, preferably has a texture developed in an orientation {110}<001>. The {110} <001> orientation means a crystal orientation (a Goss orientation), where a {110} surface is aligned parallel to the sheet steel surface, and a geometry axis <100> is aligned in the rolling direction. . on the plate

36 / 55 oriented grain electric steel, the magnetic properties are preferably improved by controlling the crystal orientation of the base steel sheet to the Goss orientation.

[00130] The texture of the base steel sheet can be measured by a general analysis method. For example, it can be measured by an X-ray diffraction method (a Laue method). The Laue method is a method in which a sheet of steel is vertically irradiated with an X-ray beam and transmitted or reflected diffraction spots are analyzed. The crystal orientation of a place to which the X-ray beam is radiated can be identified by analyzing the diffraction points. When the diffraction points are analyzed at a plurality of locations by changing an irradiation position, the crystal orientation distribution at each of the irradiation positions can be measured. The Laue method is a suitable method for measuring the crystal orientation of a coarse-grained metal structure. [Grain-oriented electric steel sheet manufacturing method]

[00131] In the following, a method for manufacturing an electrical steel sheet in accordance with the present invention will be described. A method for manufacturing a grain-oriented electrical steel sheet in accordance with the present invention is not limited to the following method. The following manufacturing method is an example for manufacturing the grain oriented electric steel steel sheet according to the present embodiment.

[00132] The grain-oriented electrical steel sheet, according to the present embodiment, can be manufactured without the forsterite film, with a texture developed in the {110}<001> orientation (i.e., suppressing the formation of the film of forsterite during completion of annealing or removing the forsterite film after final annealing), and forming the intermediate layer and insulation coating) on the base steel sheet using the base steel sheet with the groove as a material

37 / 55 starting.

[00133] In order to produce the base steel sheet with the texture developed in the {110} <001> orientation without the presence of the forsterite film, for example, the following processes are carried out. The absence of the forsterite film can be determined by looking at the cross-sectional structure using the SEM, TEM or similar described above. For example, in observing the cross-sectional structure using the SEM or TEM described above, when the forsterite film is not present continuously in the form of a film or when the average film thickness is 0.1 or less, even if the forsterite film is present in the form of a film, it can be determined that the forsterite film is not present. An average thickness of the forsterite film can be obtained in the same way as the average thickness of the insulation coating and the intermediate layer.

[00134] A piece of silicon steel containing 0.8 to 7.0% by mass of Si, preferably a piece of silicon steel containing 2.0 to 7.0% by mass of Si is hot rolled, the sheet Steel sheet after hot rolling is annealed as needed, and then the annealed steel sheet is cold rolled once or twice or more with intermediate annealing interposed between them to finish the steel sheet to a final thickness. Next, in addition to decarburization, primary recrystallization is promoted by subjecting the final thickness steel sheet to decarburization annealing, and an oxide layer is formed on the surface of the steel sheet.

[00135] Next, an annealing separator containing magnesia as a main component is applied to the surface of the steel sheet with the oxide layer and is dried, and after drying, the steel sheet is wound into a coil format. Then, the coiled steel sheet is subjected to final annealing (secondary recrystallization). A forsterite film composed mainly of a forsterite (Mg2SiO4) is formed on the surface

38 / 55 of the steel sheet during final annealing. This forsterite film is removed by pickling, grinding or the like. After removal, the steel sheet surface is preferably smoothed by chemical or electrolytic polishing.

[00136] On the other hand, as per the annealing separator described above, an annealing separator containing alumina instead of magnesia as a main component can be used. The annealing separator containing alumina as a main component is applied to the surface of the steel sheet with an oxide layer, dried, and after drying, the steel sheet is wound into a coil format. Then, the coiled steel sheet is subjected to final annealing (secondary recrystallization). When the annealing separator containing alumina as a main component is used, even when the final annealing is carried out, the film formation of inorganic mineral substance such as forsterite on the surface of the steel sheet is suppressed. After final annealing, the surface of the steel sheet is preferably smoothed by chemical or electrolytic polishing.

[00137] In order to form the intermediate layer on the base steel sheet which has no forsterite film and has the texture developed in the {110}<001> orientation, for example, the following process is carried out. The intermediate layer is formed, for example, on the base steel sheet on which the groove is formed.

[00138] The base steel sheet, from which the film of inorganic mineral substance such as a forsterite is removed, or the base steel sheet, on which the film formation of the inorganic mineral substance such as a forsterite is suppressed, is annealed in an atmospheric gas with a controlled dew point to form the intermediate layer mainly composed of a silicon oxide on the surface of the base steel sheet. In some cases, annealing cannot be carried out after the final annealing, and the insulation coating may be formed on the surface of the sheet metal.

39 / 55 base steel after final annealing.

[00139] The annealing atmosphere is preferably a reducing atmosphere, so that the inner part of the steel sheet is not oxidized, and particularly preferably an atmosphere of nitrogen mixed with hydrogen. For example, an atmosphere where hydrogen:nitrogen is 80 to 20%: 20 to 80% (100% in total), and the dew point is -20 to 2°C is preferable.

[00140] The thickness of the intermediate layer is controlled by appropriately setting an annealing temperature, a retention time, and one or more dew points of the annealing atmosphere. The thickness of the intermediate layer is preferably from 2 to 400 nm on average from the point of view to ensure the coating adhesion of the insulation coating. More preferably, it is from 5 to 300 nm.

[00141] In some cases, annealing cannot be carried out after final annealing, and the intermediate layer and insulation coating can be formed simultaneously during annealing, after a solution-forming insulation coating is applied to the surface of the steel sheet. base after final annealing. In this case, the intermediate layer and the insulating coating are formed simultaneously on the base steel sheet on which the grooves are formed.

[00142] In order to form a groove in the base steel sheet, for example, the following processes are carried out. The groove is formed by irradiating the steel sheet after cold rolling and before the intermediate layer is formed (eg after cold rolling before decarburization annealing) with a laser beam. The method for forming the groove is not limited to laser beam radiation and may be, for example, mechanical cutting, engraving or the like.

[00143] In order to form an insulating coating on the base steel sheet, in which the forsterite film does not exist and the groove is formed, for example, the insulating coating forming process is

40 / 55 performed.

[00144] An insulation coating forming solution containing at least one of phosphate and colloidal silica as a main component is applied to the base steel sheet, and the base steel sheet is soaked for 10 seconds or more and 120 seconds or minus over a temperature range of 800°C or greater and 1000°C or less in an atmospheric gas containing hydrogen and nitrogen and with an oxidation degree of PH2O/PH2 set to 0.001 or greater and 0.15 or less.

[00145] Steel sheet embedded under these conditions is cooled to 500°C at a cooling rate of 5°C/s or more and 30°C/s or less. The PH2O/PH2 oxidation degree at the time of cooling can be set to the same as the PH2O/PH2 oxidation degree at the time of soaking (i.e. 0.001 or more and 0.15 or less), and may be less than the degree of PH2O/PH2 oxidation at the time of soaking.

[00146] While phosphate, phosphates like Mg, Ca, Al and Sr are preferable, and among them, aluminum phosphate salt is more preferable. In particular, it is not limited to colloidal silica with specific properties. A particle size is also not particularly limited to a specific particle size, but is preferably 200 nm (numerical average particle diameter) or less. When the particle size exceeds 200 nm, it may precipitate in a coating liquid. In addition, the coating liquid may further contain chromic anhydride or chromate.

[00147] The insulation coating forming solution is not particularly limited, but it can be applied to the surface of the base steel sheet by, for example, a wet coating method like a roll coating.

[00148] The base steel sheet, to which the insulation coating forming solution is applied, is heat treated at a temperature of 800 to 1000°C to bake the insulation coating onto the steel sheet, and the

41 / 55 tension is applied to the steel sheet due to a difference in coefficient of thermal expansion.

[00149] When a heat treatment temperature of the insulation coating is less than 800°C, sufficient film tension cannot be obtained. In addition, when the heat treatment temperature of the insulation coating exceeds 1000°C, the phosphate is decomposed, the coating formation is poor, and sufficient film tension cannot be obtained. The heat treatment time is preferably 10 seconds or more and 120 seconds or less. When the heat treatment time is less than 10 seconds, the voltage may decrease. When the heat treatment time exceeds 120 seconds, productivity will decrease.

[00150] The degree of oxidation of the atmosphere in the soaking time is set to a value in a range of 0.001 to 0.15. When the degree of oxidation of the atmosphere is less than 0.001, the middle layer can become thin. On the other hand, when greater than 0.15, the intermediate layer and the internally oxidized layer can become thick. In addition, the embedded base steel sheet is cooled to 500°C at a cooling rate of 5°C/s or more and 30°C/s or less.

[00151] When the cooling rate is less than 5°C/s, the productivity will decrease. Furthermore, when the cooling rate is greater than 30°C/s, many vacuums are generated in the insulation coating.

[00152] In addition, setting the degree of oxidation of the atmosphere at the time of cooling to be lower than the degree of oxidation of the atmosphere at the time of soaking is effective in the suppression thickening of the intermediate layer and the internally oxidized layer and in the generation of vacuums in the insulation coating, which is preferable.

[00153] When the insulation coating is formed under such conditions, good adhesion of the insulation coating can be ensured, and

42 / 55 a good reduction in iron loss can be obtained.

[00154] In the example described above, the groove is formed in the steel sheet after cold rolling and before the formation of the intermediate layer, but the groove can be formed at any stage after the cold rolling and before the formation of the coating. isolation.

[00155] Above, although the example in which the insulating coating is formed after forming the groove has been described, the groove can be formed in the base steel sheet on which the intermediate layer and the insulating coating are formed, and the intermediate layer and insulation coating can be formed further for the purpose of covering the base steel sheet by forming the groove. In that case, the insulation coating forming process of each of the stages can be carried out by the process described above, or the final insulation coating forming process can be carried out by the process described above. That is, at least the final insulating coating forming process can be carried out by the step described above, and the bottom insulating coating forming process can be carried out by a conventional process.

[00156] The line segment ratio of the internally oxidized part, the depth of the groove (that is, the depth in the plate thickness direction of the base steel plate from the surface of the base steel plate other than the base part groove to the base portion of the groove part), the average thickness of the insulation coating (and the depth in the sheet thickness direction of the base steel sheet from the surface of the insulation coating from the groove part to the groove part) and groove shape (e.g. groove continuity or the like) can be adjusted by adjusting the manufacturing conditions described above as appropriate. Since each of the manufacturing conditions affects each other in a complicated way, it cannot be

43 / 55 said in one word, but, for example, the line segment ratio of the internally oxidized part can be adjusted by the degree of oxidation of the atmospheric gas (a ratio of partial pressure of water vapor to partial pressure of hydrogen) during the process of forming insulation coating. As the degree of oxidation becomes higher, the thread seed ratio tends to increase. Furthermore, in the case of laser beam radiation, the groove depth can be adjusted by laser beam energy, radiation time and the like. In the case of mechanical cutting, the groove depth can be adjusted by adjusting a shape of a cutting tooth, a pressing force of the cutting tooth and the like. In the case of engraving, the groove depth can be adjusted by adjusting an engraving solution concentration, engraving temperature, engraving time and the like. The average thickness of the insulation coating can be adjusted by adjusting a solid content ratio of the insulation coating forming solution, an amount of coating and the like. In the case of laser beam radiation, the groove shape can be adjusted by a range of laser beam radiation and the like. In the case of mechanical cutting radiation, the groove shape can be adjusted by the shape of the cutting tooth and the like. In the case of engraving, the groove shape can be adjusted by a resistance shape.

[00157] Each layer of grain oriented electrical steel sheet in accordance with the present embodiment is observed and measured as follows.

[00158] A test piece is cut from the grain-oriented electrical steel sheet, and a coating structure of the test piece is observed with a scanning electron microscope or a transmission electron microscope.

[00159] Specifically, first, the test piece is cut so that a cutting direction is parallel to the thickness direction

44/55 sheet (in detail, the test piece is cut so that a cut surface is parallel to the sheet thickness direction and perpendicular to the rolling direction), and a cross-sectional structure of the cut surface is observed by SEM at a magnification where each of the layers is included in the observation field of view. It is possible to infer how many layers the cross-sectional structure includes by looking at a composite image of backscattered electrons (a COMPO image).

[00160] In order to identify each of the layers in the cross-sectional structure, a line analysis is performed in the sheet thickness direction, and a quantitative analysis of the chemical composition of each of the layers is performed using an X-ray spectroscopy by energy dispersive (SEM-EDS.

[00161] The elements to be analyzed quantitatively are five elements. Fe, Cr, P, Si and O. The “atomic %” described below is not an absolute value of atomic %, but a relative value calculated based on the X-ray intensity corresponding to the five elements. In the following, the specific numerical values when the relative values are calculated using the device described above or similar as shown.

[00162] First, the base steel sheet, the intermediate layer and the insulating cladding are identified as follows based on the observation results of the COMPO image and the SEM-EDS quantitative analysis results. That is, when it is assumed that there is a region where the Fe content is 80% atomic or more and an O content is less than 30% atomic excluding measurement noise, and a line segment (a thickness) in the scan line of the line analysis that corresponds to this region is 300 nm or more, this region is determined as the base steel sheet, and regions that exclude the base steel sheet are determined as the intermediate layer and cladding of isolation.

[00163] As a result of observing the region excluding the steel plate

45 / 55 basis identified above, when there is a region where a P content is 5% atomic or more, and the O content is 30% atomic or more excluding measurement noise, and also the line segment (the thickness) in the scan line of the line analysis that corresponds to this region is 300 nm or more, this region is determined as the insulation coating.

[00164] When the region that is the insulation coating described above is identified, precipitates or inclusions contained in the film are not included in targets for determination, and the region that satisfies the quantitative analysis results described above, since the matrix phase is determined to be the insulating coating. For example, when it is confirmed from the COMPO image or the line analysis results that precipitates or inclusions are present in the line analysis scan line, the determination is made based on the quantitative analysis results, as the phase of matrix without this region being included in the targets. The precipitates or inclusions can be distinguished from the matrix phase by a contrast in the COMPO image and can be distinguished from the matrix phase by the amount of constituent elements present in the quantitative analysis results.

[00165] When there is the region that excludes the base steel sheet and insulation coating identified above, and the line segment (the thickness) in the line analysis scan line that corresponds to that region is 300 nm or further, this region is determined as the middle layer. The middle layer can satisfy an average Si content of 20 atomic% or more and an average O content of 30 atomic% or more as a global average (e.g. the arithmetic mean of the atomic % of each of the elements measured at each one of the measurement points on the scan line). The intermediate layer quantitative analysis results are quantitative analysis results such as the matrix phase, which does not include analysis results of the precipitates or inclusions contained in the layer.

46 / 55 intermediate.

[00166] The identification of each of the layers and the thickness measurement by the above-described COMPO image observation and SEM-EDS quantitative analysis are performed at five or more locations with different observation fields of view. An arithmetic mean value is obtained from values that exclude a maximum value and a minimum value between the thickness of the layers obtained at five or more locations in total, and this average value is used depending on the thickness of each of the layers. However, preferably, the thickness of the oxide film, which is the intermediate layer, is measured at a location where it can be determined, which is an external oxidation region and not an internal oxidation region while a morphology is observed, and a average value of the same is obtained.

[00167] In the groove part, the average thickness of the intermediate layer and the average thickness of the insulation coating can be calculated by the same method.

[00168] When there is a layer where the line segment (the thickness) in the line analysis scan line is less than 300 nm in at least one of the five or more observation fields of view described above, a corresponding layer is observed in detail with the TEM, and the identification of the corresponding layer and the measurement of the thickness are carried out by the TEM.

[00169] More specifically, a test piece that includes a layer to be observed in detail using TEM is cut by focused ion beam (FIB) processing so that a cut direction is parallel to the plate thickness direction (specifically , the test piece is cut so that a cut surface is parallel to the sheet thickness direction and perpendicular to the rolling direction), and the cross-sectional structure of that cut surface (a brightfield image) is observed by TEM of scan (STEM) at a magnification where the corresponding layer is

47/55 included in the observation field of view. When each of the layers is not included in the observation field of view, the cross-sectional structure is observed in a plurality of continuous fields of view.

[00170] In order to identify each of the layers in the cross-sectional structure, line analysis is performed in the sheet thickness direction using TEM-EDS, and quantitative analysis of the chemical composition of each of the layers is performed. The elements to be analyzed quantitatively are five elements Fe, Cr, P, Si and O.

[00171] Each of the layers is identified and the thickness of each of the layers is measured based on the TEM brightfield image observation results and the TEM-EDS quantitative analysis results described above. The method for identifying each of the layers and the method for measuring the thickness of each of the layers using TEM can be performed according to the method described above using SEM.

[00172] Specifically, the region where the Fe content is 80% atomic or more and the O content is less than 30% atomic excluding measurement noise is determined as per the base steel plate, and the regions that exclude the base steel sheet are determined according to the intermediate layer and the insulation coating.

[00173] In the region excluding the base steel plate identified above, the region where the P content is 5 atomic% or more and the O content is 30 atomic% or more excluding measurement noise is determined as per the insulation coating. When the region described above, which is the insulating coating, is identified, precipitates or inclusions contained in the insulating coating are not included in targets for determination, and the region that satisfies the result of quantitative analysis described above, since the phase of matrix is determined as the insulation coating.

[00174] The region excluding the base steel sheet and the insulation coating identified above is determined as per the layer

48 / 55 intermediate. The middle layer can satisfy an average Si content of 20% atomic or more and an average O content of 30% atomic or more as an average of the entire middle layer. The above-described quantitative analysis results of the intermediate layer do not include the analysis results of the precipitates or inclusions contained in the intermediate layer and are the quantitative analysis results according to the matrix phase.

[00175] For the interlayer and insulation cladding identified above, the line segment (the thickness) is measured on the line analysis scan line described above. When the thickness of each of the layers is 5 nm or less, it is preferable to use a TEM with a spherical aberration correction function from a spatial resolution point of view. Furthermore, when the thickness of each of the layers is 5 nm or less, a point analysis can be performed in the sheet thickness direction at intervals of, for example, 2 nm, the line segment (the thickness) of each one of the layers can be measured, and that line segment can be taken as the thickness of each of the layers. For example, when TEM with spherical aberration correction function is used, an EDS analysis can be performed with a spatial resolution of about 0.2 nm.

[00176] Observation and measurement with the TEM was performed at 5 or more locations with different observation fields of view, and an arithmetic mean value is calculated from the values obtained excluding the maximum and minimum values of the measurement results obtained in five or more locations in total, and the average value is adopted as the average thickness of the corresponding layer. Also, in the groove part, the average thickness of the intermediate layer and the average thickness of the insulation coating can be calculated by the same method.

[00177] On grain-oriented electrical steel sheet, according to the above described embodiment, once the intermediate layer is present

49 / 55 to be in contact with the base steel sheet, and the insulation coating is present to be in contact with the intermediate layer, when each of the layers is identified by the determination standards described above, there is no different layer of the base steel sheet, the intermediate layer, and the insulating cladding.

[00178] In addition, the Fe, P, Si, O, Cr contents described above and the like contained in the base steel sheet, the intermediate layer and the insulation coating are the determination standards to identify the steel sheet of base, the intermediate layer and the insulation coating and obtain their thickness.

[00179] When the coating adhesion of the oriented grain electrical steel sheet insulation coating according to the above described embodiment is measured, it can be evaluated by performing a bending adhesion test. Specifically, a test piece in flat plate format of 80 mm x 80 mm is wound around a circular bar with a diameter of 20 mm and is then extended flat. Then, an area of the insulation coating that is not stripped from the electrical steel sheet is measured, and a value obtained by dividing the area that is not stripped by an area of the steel sheet is defined as a ratio of residual coating area (% ) to assess the coating adhesion of the insulation coating. For example, it can be calculated by placing a clear film with a 1 mm grid scale on the test piece and measuring the area of the insulation coating that is not peeled.

[00180] Iron loss (W17/50) from grain oriented electrical steel sheet is measured under conditions of an AC frequency of 50 hertz and an induced magnetic flux density of 1.7 tesla. [Examples]

[00181] In the following, while the effect of an aspect of the present invention is described in more detail by examples, the conditions in the examples are

50 / 55 an example condition adopted to confirm the feasibility and effect of the present invention, and the present invention is not limited to that one example condition.

[00182] In the present invention, various conditions can be adopted while the essence of the present invention is not deviated, and the object of the present invention is achieved.

[00183] Steel parts of material with the component composition shown in Table 1 were soaked at 1150°C for 60 minutes and then subjected to hot rolling to obtain a hot rolled steel sheet with a thickness of 2.3 mm. Next, the hot-rolled steel sheet was subjected to hot band annealing in which it is held at 1120°C for 200 seconds, immediately cooled, held at 900°C for 120 seconds, and then rapidly cooled. The hot strip annealed steel sheet was pickled and then subjected to cold rolling to obtain a hot rolled steel sheet with a final sheet thickness of 0.23 mm. The groove was formed on the surface of this cold-rolled steel sheet by irradiation with a laser beam. [Table 1] Material Component Composition (% by mass) Steel part Si C Al Mn S N A 3.25 0.052 0.029 0.110 0.007 0.008

[00184] This cold-rolled steel sheet (hereinafter referred to as a “steel sheet”) after groove formation was subjected to decarburization annealing in which it is maintained in a 75% hydrogen:nitrogen atmosphere: 25% at 850°C for 180 seconds. The steel sheet after decarburization annealing was subjected to nitriding annealing in which it is kept in a mixed atmosphere of nitrogen, nitrogen and ammonia at 750ºC for 30 seconds to adjust the nitrogen content of the steel sheet to 230 ppm.

[00185] An annealing separator containing alumina as a main component is applied to the steel sheet after annealing by

51 / 55 nitriding, and then the steel sheet is heated to 1200°C at a heating rate of 15°C/hour in a mixed atmosphere of hydrogen and nitrogen for final annealing. Then, the steel sheet was subjected to purification annealing in which it is kept at 1200°C for 20 hours in a hydrogen atmosphere. Then, the steel sheet was naturally cooled to prepare a base steel sheet with a smooth surface.

[00186] The base steel sheet was annealed under conditions of 25% N2+75% H2 , dew point: atmosphere at -2ºC, 950ºC and 240 seconds, and an intermediate layer with an average thickness of 9 nm was formed on the surface of the base steel plate.

[00187] Next, the insulation coating was formed on the base steel sheet in which the groove was formed by irradiating with the laser beam under the conditions shown in Table 2. Table 2 shows the cooking and cooling conditions of the insulation coating. A retention time was 10 to 120 seconds. [Table 2] Insulation coating forming process Heating/Soaking Heating/cooling Temperature Speed Degree of Time Degree of Cooling (℃) Oxidation (s) Oxidation (℃/s) Example 1 850 0.0012 120 0.0012 20 Example 2 850 0.0120 120 0.0120 20 Example 3 850 0.0300 120 0.0300 20 Example 4 850 0.1000 120 0.1000 20 Example 5 850 0.1500 120 0.1500 20 Example 6 900 0.0120 60 0.0120 4 Example 7 900 0.0120 60 0.0120 10 Example 8 900 0.0120 60 0.0120 15 Example 9 900 0.0120 60 0.0120 30 Example 10 850 0.0300 30 0.0300 20 Example 11 850 0.0300 30 0.0300 20 Example 12 850 0.0300 30 0.0300 20 Example 13 850 0.0300 15 0.0300 20 Example 14 850 0.0300 15 0.0120 20 Example 15 850 0.0300 0.0012 20 Example 16 850 0.1500 120 0.1500 20 Comparative Example 1 850 0.0002 60 0.0002 20 Comparative Example 2 850 0.2500 60 0.2500 20 Comparative Example 3 900 0.0120 60 0.0120 50

[00188] Based on the observation described above and the method of

52 / 55 measurement, a test piece was cut from a grain-oriented electrical steel sheet on which an insulating coating is formed, the coating structure of the test piece was observed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the state of the voids in the insulation coating, the depth of the groove part, the thickness of the intermediate layer, and the thickness of the insulation coating were measured.

The specific method is as described above.

The results thereof are shown in Table 3. When the presence or absence of the forsterite film was confirmed by the observation method described above, the forsterite film was not present in any of the examples and comparative examples.

In table 3, the “internally oxidized part presence rate” indicates the “line segment ratio of the internally oxidized part”, the “groove part depth” indicates the “depth in the baseplate plate thickness direction from the base steel plate surface different from the groove part to the base portion of the groove part”, the “insulation coating thickness of the groove part” indicates “the depth in the plate thickness direction of the plate of base steel from the surface of the insulating coating of the groove part to the bottom of the groove part", and the "insulation coating thickness different from the groove part" indicates the "average thickness of the insulation coating different from the furrow part”. [Table 3] Thickness Ratio Thickness Ratio Thickness of layer average Depth Presence Ratio coating intermediate coating of part area part and part of insulation groove insulation and thickness internally of part groove voids of different from average from layer (%) oxidized (μm) groove part of intermediate groove different (%) (μm) (μm) from groove part Example 1 6 0.9 3 22 26.1 3.1 Example 2 7 1.1 5 22 25.9 2.9 Example 3 6 1.2 6 22 25.8 2.8 Example 4 9 1.2 8 22 26.0 3.0 Example 5 8 1.3 16 22 25.8 2.8 Example 6 2 1.2 6 26 29.3 2.3 Example 7 4 1.1 5 26 29.4 2.4 Example 8 7 1.3 7 26 29.4 2.4

53 / 55 Thickness Ratio Thickness Ratio Thickness of average layer Ratio of presence of Depth coating Intermediate coating of part area of part and part of insulation of groove insulation and thickness internally of groove of part of different from the average of the layer (%) oxidized (μm) groove intermediate groove part different (%) (μm) (μm) from groove part Example 9 15 1.2 5 26 29.5 2.5 Example 10 4 1.0 5 12 16 .2 3.2 Example 11 5 1.1 6 17 21.1 3.1 Example 12 9 1.1 10 32 36.1 3.1 Example 13 11 1.3 13 38 42.2 3.2 Example 14 8 1.1 7 38 42.2 3.2 Example 15 7 1.1 5 38 42.2 3.2 Example 16 12 2.7 18 38 42.1 3.1 Example 8 0.4 3 22 25.8 2 .8 comparative 1 Example 10 3.1 28 22 26.1 3.1 comparative 2 Example 20 1.3 9 26 29.6 2.6 comparative 3

[00189] Next, an 80mm x 80mm test piece was cut from the grain-oriented electrical steel sheet, on which the insulation coating was formed, wound around a circular bar with a diameter of 20mm, and then extended flat. Then, the area of the insulation coating, which is not stripped from the electrical steel sheet, was measured, and the residual coating area ratio (%) was calculated.

[00190] In addition, the results thereof are shown in Table 4.

[00191] The adhesion of the insulation coating was evaluated in three stages. “A (Excellent)” means the residual coating area ratio is 95% or more. “B (Good)” means that the residual coating area ratio is 90% or more. “C (Poor)” means that the residual coating area ratio is less than 90%. [Table 4] Iron Loss Adhesion W17/W50(W/kg) Example 1 A 0.68 Example 2 A 0.67 Example 3 A 0.67 Example 4 A 0.68 Example 5 B 0.68 Example 6 A 0 .65 Example 7 A 0.65 Example 8 A 0.67

54 / 55 Iron Loss Adhesion W17/W50(W/kg) Example 9 A 0.68 Example 10 A 0.71 Example 11 A 0.69 Example 12 A 0.69 Example 13 B 0.68 Example 14 A 0.68 Example 15 A 0.67 Example 16 B 0.70 Comparative Example 1 C 0.84 Comparative Example 2 C 0.88 Comparative Example 3 C 0.93

[00192] Furthermore, the iron loss from the grain-oriented electrical steel sheet of each of the experimental examples was measured. The results are shown in Table 4.

[00193] As can be seen from Table 4, in the grain-oriented electrical steel sheet produced by the manufacturing method of the present invention, the loss of iron was reduced. In Example 6, since the cooling rate was less than 5°C/sec, productivity was decreased, but excellent results were obtained in terms of iron loss and coating adhesion. That is, even when the cooling rate is less than 5°C/sec, the productivity is only diminished, and a grain-oriented electric steel sheet with excellent iron loss and coating adhesion can be obtained. [Industrial Applicability]

[00194] According to the present invention, it is possible to provide a grain-oriented electrical steel sheet capable of ensuring good adhesion of an insulating coating and achieving a good effect of reducing iron loss in grain-oriented electrical steel sheets. which does not have a forsterite film and has grooves formed in a base steel sheet, and a method for making such a grain steel sheet. Therefore, it has high industrial applicability. [Brief Description of Reference Symbols]

[00195] 1 Base steel sheet 2 Forsterite film

55 / 55

3 Insulating coating 4 Intermediate layer 5 Internally oxidized part 6 Interface between insulation coating and intermediate layer

Claims (7)

1. Grain-oriented electrical steel sheet with a base steel sheet, an intermediate layer arranged to be in contact with the base steel sheet, and an insulating coating arranged to be in contact with the intermediate layer, the base sheet grain-oriented electrical steel characterized in that it comprises: a surface of the base steel sheet has a groove that extends in a direction that crosses a rolling direction of the base steel sheet, wherein in a cross-sectional view from a plane parallel to the rolling direction and a sheet thickness direction of the base steel sheet, when a region between groove end portions is defined as a groove part, an average thickness of the middle layer of the groove part is 0.5 times or more and 3.0 times or less an average thickness of the intermediate layer different from the groove part, and an area ratio of voids in the insulating coating of the groove part is 15% or less. 2. Grain-oriented electrical steel sheet according to claim 1, characterized in that, in the cross-sectional view, when an internally oxidized part with a maximum depth of 0.2 μm or more is present in the steel sheet of The base of the groove part is represented by a line segment ratio at an interface between the base steel sheet and the intermediate layer, the internally oxidized part is present at 15% or less. 3. Grain-oriented electrical steel sheet according to claim 1 or 2, characterized in that, in the cross-sectional view, a depth of the base steel plate from the surface of the base steel plate different from the part of groove to a bottom portion of the groove part in the plate thickness direction of the base steel plate is 15 μm or more and 40 μm or less. 4. Grain-oriented electrical steel sheet according to any one of claims 1 to 3, characterized in that, in the cross-sectional view, an average thickness of the insulation coating other than the juice part is 0.1 μm or more and 10 μm or less, and the depth of the base steel sheet from a surface of the insulating coating of the groove part to the bottom portion of the groove part in the sheet thickness direction of the base steel sheet is of 15.1 μm or more and 50 μm or less. 5. Grain-oriented electrical steel sheet according to any one of claims 1 to 4, characterized in that the groove is provided continuously or discontinuously when viewed in a direction perpendicular to a sheet steel surface of the base. 6. A method for manufacturing grain oriented electrical steel sheet as defined in any one of claims 1 to 5, the method characterized in that it comprises: forming a groove in the base steel sheet which does not have a forsterite film and has a texture developed in an orientation {110}<001> at any stage after cold rolling and before the insulation coating is formed on the base steel sheet; and forming the intermediate layer and the insulating coating on the base steel sheet after the groove is formed, wherein in forming the insulating coating, an insulating coating forming solution is applied to the base steel sheet, and the base steel sheet is soaked at a temperature range of 800°C or greater and 1000°C or less for 10 seconds or more and 120 seconds or less in an atmospheric gas containing hydrogen and nitrogen and having an oxidation degree of PH2O /PH2 set to 0.001 or more and 0.15 or less, and the embedded base steel sheet is cooled to 500°C at a cooling rate of 5°C/s or more and 30°C/s or less. 7. Method for manufacturing the grain oriented electrical steel sheet as defined in any one of claims 1 to 5, the method characterized in that it comprises: forming the intermediate layer and the insulation coating on the base steel sheet which does not has a forsterite film and has a texture developed in {110}<001> orientation; forming a groove in the base steel sheet in which the intermediate layer and insulation coating are formed; and further forming the intermediate layer and the insulating coating on the base steel sheet in which the groove is formed, wherein, in at least the final formation of the insulating coating, an insulating coating forming solution is applied to the insulating plate. base steel, and the base steel sheet is soaked at a temperature range of 800°C or greater and 1000°C or less for 10 seconds or more and 120 seconds or less in an atmospheric gas containing hydrogen and nitrogen and with an oxidation degree of PH2O/PH2 set at 0.001 or more and 0.15 or less, and the embedded base steel sheet is cooled to 500°C at a cooling rate of 5°C/s or more and 30° C/s or less.